The spine is formed of a column of vertebra that extends between the cranium and pelvis. The three major sections of the spine are known as the cervical, thoracic and lumbar regions. There are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae, with each of the 24 vertebrae being separated from each other by an intervertebral disc. A series of about 9 fused vertebrae extend from the lumbar region of the spine and make up the sacral and coccygeal regions of the vertebral column.
The main functions of the spine are to provide skeletal support and protect the spinal cord. Even slight disruptions to either the intervertebral discs or vertebrae can result in serious discomfort due to compression of nerve fibers either within the spinal cord or extending from the spinal cord. If a disruption to the spine becomes severe enough, damage to a nerve or part of the spinal cord may occur and can result in partial to total loss of bodily functions (e.g. walking, talking, and breathing, etc. . . . ). Therefore, it is of great interest and concern to be able to both correct and prevent any ailments of the spine.
Fixation systems are often surgically implanted into a patient to aid in the stabilization of a damaged spine or to aid in the correction of other spinal geometric deformities. Spinal fixation systems are often constructed as framework stabilizing a particular section of the spine. Existing systems often use a combination of rods, plates, pedicle screws and bone hooks for fixing the framework to the affected vertebrae. The configuration required for each patient varies due to the patient's specific anatomical characteristics and ailments. For example, pedicle screws are often made available in a number of different size shanks (including lengths and widths), can be cannulated or non-cannulated, and may be designed to capture different size rods. Thus, the number of pedicle screws that may need to be provided in order to account for all desired combinations can be very costly and space prohibited.
Spinal fixation systems are often used as an adjunct to spinal fusion procedures in which implants are positioned within an intervertebral disc space to restore a desired height and/or alignment between the upper and lower vertebrae. Ultimately, bone growth across the disc space fuses the vertebrae together thereby maintaining the restored height and/or alignment. Spinal fixation systems are often used to maintain the vertebrae in the corrected position until the bone has had time to fully fuse. In many cases, the fusion implants are positioned first and the spinal fixation systems are placed subsequently. In some instances, this is necessitated by the surgical approach (e.g. anterior, posterior, lateral, etc. . . . ) and in some cases this is necessitated by the fixation system. For example, in posterior lateral interbody fusion (PLIF) and transforaminal interbody fusion (TLIF) procedures, the general size of the polyaxial pedicle screws in common use today can inhibit access to disc space if they are implanted prior to disc space preparation and implant positioning. This need to prepare the disc space and implant the interbody implant prior positioning the fixation system limits the options available to the surgeon.
The fixation system described herein is directed at eliminating, or at least improving upon, the shortcomings of the prior art.